1. Technical Field
This disclosure relates generally to ink follower compositions for use in writing instruments; e.g., ball point pens. More specifically, this disclosure relates to novel ink follower compositions containing polar additives, thickener and/or specific combinations of non-polar fluid components.
2. Background of Related Art
Ink followers, also known as "grease plugs" are generally employed in ball-point pens containing inks of low viscosity. Typically, ink followers are composed of a liquid which is thickened to a grease-like consistency via the use of a thickener. The ink follower is positioned in the ink tube behind the ink supply at the opposite end from the ball point. The ink follower thereby prevents backleakage of the ink. Ink followers, in addition to preventing backleakage, also inhibit evaporation of solvents and reduce the risk of shock breakage (i.e., the formation of air gaps in the ink tube).
U.S. Pat. Nos. 3,526,522 and 3,656,857 disclose ink follower compositions containing a liquid vehicle and solid, microscopic grains or particles of organic plastic or polymer. U.S. Pat. No. 5,348,989 discloses ink volatilization-preventing compositions that contain a slightly volatile organic liquid, a gelling agent and a polyether-modified silicone.
It would be desirable to provide an ink follower composition that does not adhere too much to the walls of the ink tube on following and that reduces the risk of shock breakage within the ink reservoir.